Methods for the preparation of cellulose fibers having superabsorbent particles adhered thereto

ABSTRACT

A method for adhering superabsorbent particles to cellulose fibers, comprising optionally treating cellulose treated with a hydrophilic polysaccharide polymer with a crosslinking agent in water to provide a first aqueous mixture; adding a plurality of superabsorbent particles to the first aqueous suspension to provide a second aqueous mixture; and mixing the second aqueous mixture with a water-miscible solvent to provide cellulose fibers having superabsorbent particles adhered thereto.

BACKGROUND OF THE INVENTION

Personal care absorbent products, such as infant diapers, adultincontinent pads, and feminine care products, typically contain anabsorbent core that includes superabsorbent polymer particlesdistributed within a fibrous matrix. Superabsorbents arewater-swellable, generally water-insoluble absorbent materials having ahigh absorbent capacity for body fluids. Superabsorbent polymers (SAPS)in common use are mostly derived from acrylic acid, which is itselfderived from petroleum oil, a non-renewable raw material. Acrylic acidpolymers and SAPs are generally recognized as not being biodegradable.Despite their wide use, some segments of the absorbent products marketare concerned about the use of nonrenewable petroleum oil derivedmaterials and their non-biodegradable nature. Acrylic acid basedpolymers also comprise a meaningful portion of the cost structure ofdiapers and incontinent pads. Users of SAP are interested in lower costSAPs. The high cost derives in part from the cost structure for themanufacture of acrylic acid which, in turn, depends upon the fluctuatingprice of petroleum oil. Also, when diapers are discarded after use theynormally contain considerably less than their maximum or theoreticalcontent of body fluids. In other words, in terms of their fluid holdingcapacity, they are “over-designed”. This “over-design” constitutes aninefficiency in the use of SAP. The inefficiency results in part fromthe fact that SAPs are designed to have high gel strength (asdemonstrated by high absorbency under load or AUL). The high gelstrength (upon swelling) of currently used SAP particles helps them toretain a lot of void space between particles, which is helpful for rapidfluid uptake. However, this high “void volume” simultaneously results inthere being a lot of interstitial (between particle) liquid in theproduct in the saturated state. When there is a lot of interstitialliquid the “rewet” value or “wet feeling” of an absorbent product iscompromised.

In personal care absorbent products, U.S. southern pine fluff pulp iscommonly used in conjunction with the SAP. This fluff is recognizedworldwide as the preferred fiber for absorbent products. The preferenceis based on the fluff pulp's advantageous high fiber length (about 2.8mm) and its relative ease of processing from a wetland pulp sheet to anairlaid web. Fluff pulp is also made from renewable and biodegradablecellulose pulp fibers. Compared to SAP, these fibers are inexpensive ona per mass basis, but tend to be more expensive on a per unit of liquidheld basis. These fluff pulp fibers mostly absorb within the intersticesbetween fibers. For this reason, a fibrous matrix readily releasesacquired liquid on application of pressure. The tendency to releaseacquired liquid can result in significant skin wetness during use of anabsorbent product that includes a core formed exclusively fromcellulosic fibers. Such products also tend to leak acquired liquidbecause liquid is not effectively retained in such a fibrous absorbentcore.

Superabsorbent composites in fiber form have a distinct advantage overparticle forms in some applications. Such superabsorbent compositefibers can be made into a pad form directly. Liquid acquisition will bemore uniform compared to a fiber pad with shifting superabsorbentparticles.

A need therefore exists for fibrous superabsorbent materials that havethe ability to have superabsorbent particles attached to the fibers.Biodegradable renewable fibers such as cellulose fiber is ideallysuitable for such a fibrous superabsorbent composite material, if it canbe treated and made to have strong affinity to superabsorbent particles.In this way, the superabsorbent material can be used in absorbentproduct designs that are efficient. These and other objectives areaccomplished by the invention set forth below.

SUMMARY OF THE INVENTION

The invention provides a method for adhering superabsorbent particles tocellulose fibers, comprising adding a plurality of superabsorbentparticles to a first aqueous mixture comprising cellulose treated with apolysaccharide polymer to provide a second aqueous mixture; and mixingthe second aqueous mixture with a water-miscible solvent to providecellulose fibers having superabsorbent particles adhered thereto. In oneembodiment, the method includes applying a crosslinking agent to thecellulose treated with the polysaccharide in the first aqueous mixtureprior to adding the particles.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a scanning electron microscope photograph (13×) ofrepresentative fibers with adhered superabsorbent particles made inaccordance with the method of the invention (Sample 3, Table 1);

FIG. 2 is a scanning electron microscope photograph (100×) ofrepresentative fibers with adhered superabsorbent particles made inaccordance with the method of the invention (Sample 3, Table 1);

FIG. 3 is a scanning electron microscope photograph (13×) ofrepresentative fibers with adhered superabsorbent particles made inaccordance with the method of the invention (Sample 4, Table 1); and

FIG. 4 is a scanning electron microscope photograph (100×) ofrepresentative fibers with adhered superabsorbent particles made inaccordance with the method of the invention (Sample 4, Table 1).

DETAILED DESCRIPTION OF THE INVENTION

In one aspect, the present invention provides a method for adheringparticles (e.g., superabsorbent particles) to cellulose fibers. Themethod includes the steps of adding a plurality of particles to a firstaqueous mixture comprising cellulose treated with a polysaccharidepolymer to provide a second aqueous mixture; and mixing the secondaqueous mixture with a water-miscible solvent to provide cellulosefibers having particles adhered thereto. In one embodiment, the methodincludes applying a crosslinking agent to the cellulose treated with thepolysaccharide in the first aqueous mixture prior to adding theparticles.

The product fibers are obtained by filtration. In one embodiment, themethod further includes the steps of drying the cellulose fibers havingparticles adhered thereto to provide partially-dried composite fibers(30-50% consistency). The partially-dried composite fibers can befiberized to provide partially-dried fiberized composite fibers. Thepartially-dried fiberized composite fibers can be further dried toprovide dried fiberized cellulose fibers having particles adheredthereto.

In the method, cellulose fibers that have been treated with ahydrophilic polysaccharide are combined with superabsorbent particles.

Although available from other sources, suitable cellulosic fibers arederived primarily from wood pulp. Suitable wood pulp fibers for use withthe invention can be obtained from well-known chemical processes such asthe kraft and sulfite processes, with or without subsequent bleaching.Pulp fibers can also be processed by thermomechanical,chemithermomechanical methods, or combinations thereof. A high alphacellulose pulp is also a suitable wood pulp fiber. The preferred pulpfiber is produced by chemical methods. Ground wood fibers, recycled orsecondary wood pulp fibers, and bleached and unbleached wood pulp fiberscan be used. Softwoods and hardwoods can be used. Suitable fibers arecommercially available from a number of companies, includingWeyerhaeuser Company. For example, suitable cellulosic fibers producedfrom southern pine that are usable with the present invention areavailable from Weyerhaeuser Company under the designations CF416, NF405,PL416, FR516, and NB416. Other suitable fibers include northern softwoodand eucalyptus fibers.

As used herein, the term “hydrophilic polysaccharide polymer” refers toany one of a variety of polysaccharide polymers that are hydrophilic andthat have a tendency to associate with cellulose. Representativehydrophilic polysaccharide polymers include natural polymers, such asgalactomannan polymers, glucomannan polymers, alginic acids,carageenans, starches and starch derivatives such as carboxymethylstarch, and hydroxyethyl starch, and cellulose derivatives such as suchas carboxymethyl cellulose, hydroxyethyl cellulose. In one embodiment,the hydrophilic polysaccharide polymer is a galactomannan polymer.Representative galactomannan polymers include guar gum, locust bean gum,and tara gum. In one embodiment, the hydrophilic polysaccharide polymeris a glucomannan polymer. Representative glucomannan polymers includekonjac gum. The cellulose treated with hydrophilic polysaccharidepolymer includes from about 1 to about 20 percent by weight hydrophilicpolysaccharide polymer based on the weight of cellulose.

The preparation of representative cellulose fibers treated with ahydrophilic polysaccharide polymer (e.g., guar gum treated cellulosefibers) is described in Example 1. In general, hydrophilicpolysaccharide polymer treated cellulose is prepared by dissolving adesired amount of the hydrophilic polysaccharide polymer in water (e.g.,10 g in 1000 mL water) to provide a solution and then adding cellulosefibers (e.g., 1.00 g) with mixing to provide a suspension. The treatedfibers are obtained by filtration and drying (e.g., 1.0% by weighthydrophilic polysaccharide polymer treated cellulose).

In one embodiment, an aqueous mixture of cellulose fibers treated with ahydrophilic polysaccharide polymer are treated with a crosslinking agentprior to the addition of the superabsorbent particles. The use of acrosslinking agent will depend on the nature of the particles to beadhered to the fibers. If the particles are highly crosslinked, addedcrosslinking agent is not required. However, if the particles are notadequately crosslinked to provide sufficient insolubility in water, thenthe crosslinking agent is used.

Suitable crosslinking agents include crosslinking agents that arereactive toward hydroxyl groups and carboxyl groups. Representativecrosslinking agents include metallic crosslinking agents, such asaluminum (III) compounds, titanium (IV) compounds, bismuth (III)compounds, boron (III) compounds, and zirconium (IV) compounds. Thenumerals in parentheses in the preceding list of metallic crosslinkingagents refers to the valency of the metal.

Representative metallic crosslinking agents include aluminum sulfate;aluminum hydroxide; dihydroxy aluminum acetate (stabilized with boricacid); other aluminum salts of carboxylic acids and inorganic acids;other aluminum complexes, such as Ultrion 8186 from Nalco Company(aluminum chloride hydroxide); boric acid; sodium metaborate; ammoniumzirconium carbonate (AZC); zirconium compounds containing inorganic ionsor organic ions or neutral ligands; bismuth ammonium citrate (BAC);other bismuth salts of carboxylic acids and inorganic acids; titanium(IV) compounds, such as titanium (IV) bis(triethylaminato)bis(isopropoxide) (commercially available from the Dupont Company underthe designation Tyzor TE); and other titanates with alkoxide orcarboxylate ligands.

The crosslinking agent is applied in an amount up to about 20 percent byweight based on the total weight of the treated cellulose fibers. Theamount of first crosslinking agent applied to the treated cellulose willvary depending on the crosslinking agent. In general, the fibers have analuminum content up to about 2.0% by weight based on the weight of thecomposite fibers for aluminum crosslinked fibers, a titanium content ofup to about 4.5% by weight based on the weight of the composite fibersfor titanium crosslinked fibers, a zirconium content of up to about 6.0%by weight based on the weight of the composite fibers for zirconiumcrosslinked fibers, and a bismuth content up to about 5.0% by weightbased on the weight of the composite fibers for bismuth crosslinkedfibers.

In the method, a plurality of superabsorbent particles is added to thefirst aqueous suspension including the cellulose treated with ahydrophilic polysaccharide polymer that has been optionally treated witha crosslinking agent, Suitable particles include those derived fromsynthetic hydrophilic polymers (e.g., superabsorbent polymers or SAPs),such as polyacrylic acids, polyacrylamides, and polyaspartic acids; andhydrophilic polymers (e.g., superabsorbent polymers) derived naturalpolymers, such as celluloses (e.g., carboxymethyl cellulose), alginates,chitosans, and starches (e.g., carboxymethyl starch). The combination ofa carboxyalkyl cellulose and either a glucomannan or galactomannanpolymer is not considered to be a superabsorbent particle in the contextof this invention.

Superabsorbent particles in the product cellulose fibers are be presentin an amount form about 50 to about 80% by weight of the product fibers.The polysaccharide treated fiber in the product cellulose fibers arepresent in an amount form about 20 to 50%, by weight of the productfibers.

The cellulose fibers having superabsorbent particles attached theretoare obtained by mixing the second aqueous mixture including theplurality of superabsorbent particles and treated cellulose with awater-miscible solvent. Suitable water-miscible solvents includewater-miscible alcohols and ketones. Representative water-misciblesolvents include acetone, methanol, ethanol, isopropanol, and mixturesthereof. In one embodiment, the water-miscible solvent is ethanol. Inanother embodiment, the water-miscible solvent is isopropanol.

The volume of water-miscible solvent added to the gel ranges from about1:1 to about 1:5 water to water-miscible solvent.

In the method, mixing the gel with the water-miscible solvent includesstirring to provide fibers with adhered superabsorbent particles. Themixing step and the use of the water-miscible solvent controls the rateof dehydration and solvent exchange and provides fiber with adheringsuperabsorbent particles. Mixing can be carried out using a variety ofdevices including overhead stirrers, Hobart mixers, Britishdisintegrators, and blenders.

Thus, in one embodiment, the invention provides a method for adheringsuperabsorbent particles to cellulose fibers, comprising adding aplurality of particles to a first aqueous mixture comprising cellulosetreated with a polysaccharide polymer to provide a second aqueousmixture; and mixing the second aqueous suspension with a water-misciblesolvent to provide cellulose fibers having superabsorbent particlesadhered thereto.

As noted above, in another embodiment, the method further comprisingadding a crosslinking agent to the cellulose treated with polysaccharidein the first aqueous suspension prior to adding the particles.

The methods of the invention provide cellulose fibers havingsuperabsorbent particles adhered thereto.

In one embodiment, the cellulose fibers having particles adheredthereto, include cellulose fibers treated with a hydrophilicpolysaccharide polymer and the adhered superabsorbent particles includesynthetic hydrophilic polymers (e.g., superabsorbent polymers or SAPs),such as polyacrylic acids, polyacrylamides, and polyaspartic acids; andhydrophilic polymers (e.g., superabsorbent polymers) derived naturalpolymers, such as celluloses (e.g., carboxymethyl cellulose), alginates,chitosans, and starches (e.g., carboxymethyl starch).

In another embodiment, the cellulose fibers having particles adheredthereto, include cellulose fibers treated with a hydrophilicpolysaccharide polymer and a crosslinking agent and the adheredsuperabsorbent particles include synthetic hydrophilic polymers (e.g.,superabsorbent polymers or SAPs), such as polyacrylic acids,polyacrylamides, and polyaspartic acids; and hydrophilic polymers (e.g.,superabsorbent polymers) derived natural polymers, such as celluloses(e.g., carboxymethyl cellulose), alginates, chitosans, and starches(e.g., carboxymethyl starch).

As noted above, suitable hydrophilic polysaccharide polymers includenatural polymers, such as galactomannan polymers, glucomannan polymers,alginic acids, carageenans, starches and starch derivatives such ascarboxymethyl starch, and hydroxyethyl starch, and cellulose derivativessuch as such as carboxymethyl cellulose, hydroxyethyl cellulose. In oneembodiment, the polysaccharide is guar gum.

For hydrophilic polysaccharide treated cellulose fibers also treatedwith a crosslinking agent suitable crosslinking agents include ofaluminum (III) compounds, titanium (IV) compounds, bismuth (III)compounds, boron (III) compounds, and zirconium (IV) compounds.Representative crosslinking agents are described above.

Representative cellulose fibers having superabsorbent particles adheredthereto are shown in FIGS. 1-4. FIG. 1 is a scanning electron microscopephotograph (13×) of representative cellulose fibers having adheredsuperabsorbent particles (Sample 3, Table 1). FIG. 2 is a scanningelectron microscope photograph (100×) of representative cellulose fibershaving adhered superabsorbent particles (Sample 3, Table 1). FIG. 3 is ascanning electron microscope photograph (13×) of representativecellulose fibers having adhered superabsorbent particles (Sample 4,Table 1). FIG. 4 is a scanning electron microscope photograph (100×) ofrepresentative cellulose fibers having adhered superabsorbent particles(Sample 4, Table 1).

The fibers are prepared by a process that includes optionally treatingan aqueous mixture of a plurality of superabsorbent particles andcellulose treated with a hydrophilic polysaccharide polymer with a metalcrosslinking agent to provide a mixture, and then further mixing themixture with a water-miscible solvent. The fibers produced by the methodare substantially insoluble in water while being capable of absorbingwater.

When a crosslinking agent is optionally used before addingsuperabsorbent particles to the aqueous solution containing thecellulose fiber treated with the hydrophilic polysaccharide polymer, theagent provides additional crosslinking of the polymers of thesuperabsorbent particles. This is suitable when the particles are notsufficiently crosslinked (or under crosslinked by design). When theparticles are highly crosslinked, this additional crosslinking is notused to prevent loss of absorbent capacity of the product compositefibers. When a crosslinking agent is optionally used, the agent can alsoprovide additional crosslinks between polymer molecules of thesuperabsorbent particles and the hydrophilic polymer bound to thecellulose fibers. To take advantage of this favorable attractionsbetween superabsorbent particles and the hydrophilic polysaccharidetreated cellulose fibers, the superabsorbent particles used should notbe highly crosslinked. The metal crosslink arises as a consequence of anassociative interaction (e.g., bonding) between functional groups on thehydrophilic polymers (e.g., carboxy, carboxylate, or hydroxyl groups)and a multi-valent metal species (see description of crosslinking agentsabove). The superabsorbent particles and the treated cellulose fibercontain hydrophilic polymers that can form metal crosslinks. Suitablemulti-valent metal species include metal ions having a valency of threeor greater and that are capable of forming an associative interactionwith a polymer (e.g., reactive toward associative interaction with thepolymer's carboxy, carboxylate, or hydroxyl groups). The polymers areintermolecularly crosslinked when the multi-valent metal species formsan associative interaction with functional groups on two or more polymermolecules. A crosslink may be formed within one polymer molecule or maybe formed between two or more polymer molecules.

The product fibers are highly absorptive. The fibers have a Free SwellCapacity of from about 30 to about 60 g/g (0.9% saline solution), aCentrifuge Retention Capacity (CRC) of from about 15 to about 35 g/g(0.9% saline solution), and an Absorbency Under Load (AUL) of from about15 to about 30 g/g (0.9% saline solution).

The product fibers are useful as a superabsorbent in personal careabsorbent products (e.g., infant diapers, feminine care products andadult incontinence products). The fibers have the ability to absorbwater, saline solutions and biological fluids such as urine and thefibrous form also helps in wicking. The fibers are useful in a varietyof other applications, including, for example, wound dressings, cablewrap, absorbent sheets or bags, and packaging materials.

The preparations of representative fibers are described in Examples 2and 3 The composition and liquid absorbent characteristics ofrepresentative fibers are summarized in the Table 1. In Table 1, for thesuperabsorbent particle and the polysaccharide polymer treatedcellulose, the values in parentheses refer to the relative weight ofeach in the composite superabsorbent fiber (wgt % total wgt);“Crosslinking agent/4 g” refers to the amount of crosslinking agentapplied per 4 g product; “SANIWET-4500” refers to a syntheticsuperabsorbent particle (a polyacrylic acid particle) commerciallyavailable from Hoechst Celanese; “NKS pulp with 10% GG” refers tonorthern kraft spruce (NKS) pulp treated with 10 weight % guar gum; and“with wash” refers to washing the treated fibers with 100% ethanol or100% isopropanol before drying.

Test Methods Free Swell and Centrifuge Retention Capacities

The materials, procedure, and calculations to determine tree swellcapacity (g/g) and centrifuge retention capacity (CRC) (g/g) were asfollows.

Test Materials:

Japanese pie-made empty tea bags (available from Drugstore.com, INPURSUIT OF TEA polyester tea bags 93 mm.×70 mm with fold-over flap.(http:www.mesh.ne.jp/tokiwa/)).

Balance (4 decimal place accuracy, 0.0001 g for air-dried superabsorbentpolymer (ADS SAP) and tea bag weights); timer; 1% saline; drip rack withclips (NLM 211); and lab centrifuge (NLM 211, Spin-X spin extractor,model 776S, 3,300 RPM, 120v).

Test Procedure:

1. Determine solids content of ADS.

2. Pre-weigh tea bags to nearest 0.0001 g and record.

3. Accurately weigh 0.2025 g.+/−0.0025 g of test material (SAP), recordand place into pre-weighed tea bag (air-dried (AD) bag weight). (ADSweight+AD bag weight=total dry weight).

4. Fold tea bag edge over closing bag.

5. Fill a container (at least 3 inches deep) with at least 2 inches with1% saline.

6. Hold tea bag (with test sample) flat and shake to distribute testmaterial evenly through bag.

7. Lay tea bag onto surface of saline and start timer.

8. Soak bags for specified time (e.g., 30 minutes).

9. Remove tea bags carefully, being careful not to spill any contentsfrom bags, hang from a clip on drip rack for 3 minutes.

10. Carefully remove each bag, weigh, and record (drip weight).

11. Place tea bags onto centrifuge walls, being careful not to let themtouch and careful to balance evenly around wall.

12. Lock down lid and start timer. Spin for 75 seconds.

13. Unlock lid and remove bags. Weigh each bag and record weight(centrifuge weight).

Calculations:

The tea bag material has an absorbency determined as follows:

Free Swell Capacity, factor=5.78

Centrifuge Capacity, factor 0.50

Z=Oven dry SAP wt (g)/Air dry SAP wt (g)

Free Capacity (g/g):

$\frac{\begin{matrix}{\lbrack {( {{{drip}\mspace{14mu} {wt}\mspace{11mu} (g)} - {{dry}\mspace{14mu} {bag}\mspace{14mu} {wt}\; (g)}} ) - ( {{AD}\mspace{14mu} {SAP}\mspace{14mu} {wt}\mspace{11mu} (g)} )} \rbrack -} \\( {{dry}\mspace{14mu} {bag}\mspace{14mu} {wt}\mspace{11mu} (g)*5.78} )\end{matrix}}{( {{AD}\mspace{14mu} {SAP}\mspace{14mu} {wt}\mspace{11mu} (g)*Z} )}$

Centrifuge Retention Capacity (g/g):

$\frac{\begin{matrix}{\lbrack {{{centrifuge}\mspace{14mu} {wt}\mspace{11mu} (g)} - {{dry}\mspace{14mu} {bag}\mspace{14mu} {wt}\mspace{11mu} (g)} - ( {{AD}\mspace{14mu} {SAP}\mspace{14mu} {wt}\mspace{11mu} (g)} )} \rbrack -} \\( {{dry}\mspace{14mu} {bag}\mspace{14mu} {wt}\mspace{11mu} (g)*0.50} )\end{matrix}}{( {{AD}\mspace{14mu} {SAP}\mspace{14mu} {wt}*Z} )}$

Absorbency Under Load (AUL)

The materials, procedure, and calculations to determine AUL were asfollows.

Test Materials:

Mettler Toledo PB 3002 balance and BALANCE-LINK software or othercompatible balance and software, Software set-up: record weight frombalance every 30 sec (this will be a negative number. Software can placeeach value into EXCEL spreadsheet.

Kontes 90 mm ULTRA-WARE filter set up with fritted glass (coarse) filterplate. clamped to stand; 2 L glass bottle with outlet tube near bottomof bottle; rubber stopper with glass tube through the stopper that fitsthe bottle (air inlet); TYGON tubing; stainless steel rod/plexiglassplunger assembly (71 mm diameter); stainless steel weight with holedrill through to place over plunger (plunger and weight=867 g); VWR 9.0cm filter papers (Qualitative 413 catalog number 28310-048) cut down to80 mm size; double-stick SCOTCH tape; and 0.9% saline.

Test Procedure:

1. Level filter set-up with small level.

2. Adjust filter height or fluid level in bottle so that fritted glassfilter and saline level in bottle are at same height.

3. Make sure that there are no kinks in tubing or air bubbles in tubingor under fritted glass filter plate.

4. Place filter paper into filter and place stainless steel weight ontofilter paper.

5, Wait for 5-10 min while filter paper becomes fully wetted and reachesequilibrium with applied weight.

6. Zero balance.

7. While waiting for filter paper to reach equilibrium prepare plungerwith double stick tape on bottom.

8. Place plunger (with tape) onto separate scale and zero scale.

9. Place plunger into dry test material so that a monolayer of materialis stuck to the bottom by the double stick tape.

10. Weigh the plunger and test material on zeroed scale and recordweight of dry test material (dry material weight 0.15 g+/−0.05 g).

11. Filter paper should be at equilibrium by now, zero scale.

12. Start balance recording software.

13. Remove weight and place plunger and test material into filterassembly.

14. Place weight onto plunger assembly.

15. Wait for test to complete (30 or 60 min)

16. Stop balance recording software.

Calculations:

-   -   A=balance reading (g)*−1 (weight of saline absorbed by test        material)    -   B=dry weight of test material (this can be corrected for        moisture by multiplying the AD weight by solids %).    -   AUL (g/g)=A/B (g 1% saline/1 g test material)

The following examples are provided for the purpose of illustrating, notlimiting, the invention.

EXAMPLES Example 1 The Preparation of Representative Guar Gum TreatedCellulose Fibers

In this example, the preparation of representative guar gum treatedcellulose fibers is described.

Guar gum (4.0 g) was dissolved in 3200 ml of deionized water. Northernkraft spruce (NKS) pulp (40.0 g) was dispersed in the guar gum solutionand oven dried at 105° C. This material was used for bindingsuperabsorbent composite particles.

Example 2 The Preparation of a Representative Fibrous SuperabsorbentComposite

In this example, the preparation of a representative fibroussuperabsorbent composite containing cellulose and commercialsuperabsorbent particles crosslinked with aluminum sulfate.

Aluminum sulfate octadecahydrate 0.035 g was dissolved in 50 ml ofdeionized water at 80° C. Guar gum treated cellulose fiber (prepared asdescribed as in Example 1) 1.2 g was then dispersed in the aluminumsulfate solution for 15 minutes. Commercial superabsorbent particles(SANWET IM-4500 from Hoechst Celanese) 2.8 g was added to the fiberslurry and mixed for 2 minutes. To the swollen mass of fiber gel wasadded 150 ml of isopropanol and mixed for 5 minutes to obtain compositefiber with attached superabsorbent particles. The composite fiberobtained was then filtered. The fiber mass was partially dried in theoven at 66° C., The fiber mass was then fiberized and dried in the ovenat 66° C.

T-bag test gave free swell of 39.75 g/g; centrifuge capacity of 19.86g/g; and AUL of 27.36 g/g (at 0.3 psi) for 0.9% saline solution.

Example 3 The Preparation of a Representative Fibrous SuperabsorbentComposite

In this example, the preparation of a representative fibroussuperabsorbent composite containing cellulose and commercialsuperabsorbent particles without added crosslinking agent.

Guar gum treated cellulose fiber (prepared as described as in Example 1)1.2 g was then dispersed in 50 ml of deionized water at 80° C. for 15minutes. Commercial superabsorbent particles (SANWET IM-4500 fromHoechst Celanese) 2.8 g was added to the fiber slurry and mixed for 2minutes. To the swollen mass of fiber gel was added 150 ml ofisopropanol and mixed to obtain composite fiber with attachedsuperabsorbent particles. The composite fiber obtained was the filtered.The fiber mass was partially dried in the oven at 66° C. The fiber masswas then fiberized and dried in the oven at 66° C.

T-bag test gave free swell of 40.50 g/g; centrifuge capacity of 23.54g/g; and AUL of 28.15 g/g (at 0.3 psi) for 0.9% saline solution.

TABLE 1 Composition and Absorbent Properties of Composite SuperabsorbentFiber from Synthetic Superabsorbent and Galactomannan Treated CellulosePolysaccharide polymer treated Superabsorbent particle cellulose FreeSwell CRC AUL Sample (wgt % total wgt) (wgt % total wgt) Crosslinkingagent/4 g (g/g) (g/g) (g/g) 1 SANWETIM-4500 (50%) NKS pulp with 10% GG(50%) 0.017 g Al₂(SO₄)₃ with wash 35.3 15.62 23.31 2 SANWETIM-4500 (50%)NKS pulp with 10% GG (50%) — 33.95 16.61 23.8 3 SANWETIM-4500 (70%) NKSpulp with 10% GG (30%) 0.017 g Al₂(SO₄)₃ with wash 39.75 19.86 27.36 4SANWETIM-4500 (70%) NKS pulp with 10% GG (30%) — 40.5 23.54 28.15

White illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

1. A method for adhering superabsorbent particles to cellulose fibers,comprising: (a) adding a plurality of superabsorbent particles to afirst aqueous mixture comprising cellulose treated with a polysaccharidepolymer to provide a second aqueous mixture; and (b) mixing the secondaqueous mixture with a water-miscible solvent to provide cellulosefibers having superabsorbent particles adhered thereto.
 2. The method ofclaim 1 further comprising drying the cellulose fibers having particlesadhered thereto to provide a partially-dried composite fibers.
 3. Themethod of claim 2 further comprising fiberizing the partially-driedcomposite fibers to provide partially-dried fiberized composite fibers.4. The method of claim 3 further comprising drying the partially-driedfiberized composite fibers to provide dried fiberized composite fibers.5. The method of claim 1, wherein the polysaccharide is selected fromthe group consisting of galactomannan polymers, glucomannan polymers,alginic acids, carageenans, carboxymethyl cellulose, hydroxyethylcellulose, starch, carboxymethyl starch, and hydroxyethyl starch.
 6. Themethod of claim 1, wherein the polysaccharide comprises guar gum.
 7. Themethod of claim 1, wherein the particles are selected from the groupconsisting of synthetic polymers, carboxyalkyl cellulose polymers,carboxyalkyl starch polymers, alginates, chitosans, and starches.
 8. Themethod of claim 7, wherein the synthetic polymers are selected from thegroup consisting of polyacrylic acid polymers, polyacrylamide polymers,and polyaspartic acid polymers.
 9. The method of claim 1 furthercomprising applying a crosslinking agent to the cellulose treated withpolysaccharide in the first aqueous mixture prior to adding theparticles.
 10. The method of claim 9, wherein the crosslinking agent isselected from the group consisting of aluminum (III) compounds, titanium(IV) compounds, bismuth (III) compounds, boron (III) compounds, andzirconium (IV) compounds.
 11. The method of claim 9 further comprisingdrying the cellulose fibers having particles adhered thereto to providea partially-dried composite fibers.
 12. The method of claim 11 furthercomprising fiberizing the partially-dried cellulose fibers to providepartially-dried fiberized composite fibers.
 13. The method of claim 12further comprising drying the partially-dried fiberized cellulose fibersto provide dried fiberized composite fibers.
 14. The method of claim 9,wherein the polysaccharide is selected from the group consisting ofgalactomannan polymers, glucomannan polymers, alginic acids,carageenans, carboxymethyl cellulose, hydroxyethyl cellulose, starch,carboxymethyl starch, and hydroxyethyl starch.
 15. The method of claim9, wherein the polysaccharide comprises guar gum.
 16. The method ofclaim 95 wherein the particles are selected from the group consisting ofsynthetic superabsorbent polymers, carboxyalkyl cellulose polymers,carboxyalkyl starch polymers, alginates, chitosans, and starches. 17.The method of claim 9, wherein the synthetic superabsorbent polymers areselected from the group consisting of polyacrylic acid polymers,polyacrylamide polymers, and polyaspartic acid polymers.